Oncogenes, the cancer-inducing genes are known to be the normal cellular genes that become activated during carcinogenesis. Oncogenes can be activated via deregulation of their expression and/or structural alterations that change their gene products. Knowledge on regulation of oncogene expression is essential for understanding mechanisms of carcinogenesis. The long-term objectives of this proposal are to understand the regulatory mechanisms of oncogenes. The neu oncogene and the gene encoding epidermal growth factor receptor (EGF-r) are two distinct but structurally related genes. Based on published data and preliminary results shown in the proposal, a common regulatory factor required for expression of both neu and EGF-r genes may be missing in the NR-6 cell line. The specific aims of the proposed project are: firstly, to identify the common factor(s) that is missing in the NR-6 cell line and required for the expression of neu and EGF-r genes; secondly, to characterize the function of the regulatory factor; thirdly, to isolate a molecular clone of the gene encoding the regulatory factor; and finally, to search for multiple regulatory factors and DNA elements that control the expression of neu gene. The Preliminary Results described in this proposal indicate that both neu and EGF-r genes exhibit similar tissue-specific and development-specific expression patterns, suggesting the two genes may share some common factor(s) controlling their expression. The preliminary results also demonstrate that the neu gene can not be expressed in the NR-6 cell line in which the EGF- r gene is not expressed due to lack of a positive trans-acting factor(s). The results derive a hypothesis that the NR-6 cell line may lack a common factor required for expression of both neu and EGF-r genes. To confirm this hypothesis, the somatic cell fusion between Swiss 3T3 cells, in which both neu and EGF-r genes are expressed, and NR-6 cells or the neu transfectants of NR-6 cells will be carried out and the expression of neu will be examined by Northern analysis, immunoprecipitation experiments. DNA transfection will be used to isolate the molecular clone encoding the regulatory factor. In addition to clone the gene encoding this specific regulatory factor, the proposal also aims at searching for multiple regulatory factors essential for transcription of neu gene using more general approaches such as gel-retardation and in vitro transcription assays. Identification of multiple factors controlling the expression of neu gene and cloning of their genes should provide new insights in understanding the regulatory mechanisms of oncogenes.